State of the art mailing machines can perform such automatic functions as handling mail of different sizes and thicknesses, envelope sealing, mail weighing, mail stamping, and mail sorting. The typical processing sequence starts at the front end of the machine where the mail is stacked. The stacked mail is then registered against a reference wall of the machine and the next step in the process is to feed the mail to a singulator to remove individual mail pieces from the bottom of the stack and thereafter process those individual mail pieces in serial fashion through the various modules of the machine.
Special problems arise when the mail to be handled is mixed mail, meaning envelopes containing inserts that have their flaps sealed, or closed but unsealed, or open. The problems intensify when an added requirement is the ability to process envelopes of varying sizes, for example from No. 6 to No. 15, and of varying thickness, say from thin air mail with a single insert up to three-quarters of an inch. Further problems arise when an additional added requirement is high-speed processing, up to four per second. To our knowledge, there exists no mail handling machine capable of high speed processing of mixed mail of varying size and thickness.